Illegal campfires are believed to have sparked a newly discovered wildfire burning in Banff National Park.

Spotted Friday burning near the west end of Bow Lake, north of Lake Louise just west of the Icefields Parkway, the 0.5 hectare fire is being worked on by wildfire crews, said Lesley Matheson of Parks Canada.

The Bow Glacier Falls trail, the Bow Hut access route and parts of the Bow Lake trail are closed due to firefighting efforts.

The fire, which she said currently poses no threat to people or facilities, is currently under investigation by Parks Canada and the RCMP.

Matheson reminds park visitors disobeying the fire ban can be costly, with violators facing fines of as much as $25,000.

"We're still in a fire ban in almost all of the western national parks," she said.

"If the fire at Bow Lake wasn't in such a visible spot and it hadn't been spotted, there could have been some serious consequences."

A second fire was spotted in Kootenay National Park on Thursday morning, burning four kilometres south of the Crooks Meadows campground — 20 kilometres south of the Verdant Creek fire.

Promptly attended to by nearby crews, that blaze is also about half a hectare in size and isn't considered a risk to people or park facilities.

Meanwhile, crews continue to struggle against the growing Verdant Creek wildfire, burning on the British Columbia side of the Continental Divide.

Matheson said increased activity in remote southeastern areas of Mount Assiniboine Provincial Park has resulted in the two-and-a-half month old wildfire growing in size — now almost 5,000 hectares.

August's hot and dry weather has proven a frustration for crews in both B.C. and Alberta, who've been waging war against the lightning-sparked fire since July 15.

"We need a significant change in weather for this to be fully extinguished," she said.

"We need that substantial rainfall that we're probably due to get."

Meanwhile, a new blaze near Cranbrook prompted officials to close that city's international airport.

Currently under direct attack by B.C. wildfire crews, the 25-hectare fire near St. Mary's River on the Aq'am First Nation sent palls of thick smoke into the sky that cancelled all fights of the airport, according to a news release posted to the City of Cranbrook website.

Only aircraft related to firefighting efforts are permitted to use the airport.

Anybody with flights booked into Cranbrook for the long weekend is asked to contact either Pacific Coastal Airlines or Air Canada for rebooking information.